Lens system.



JDUQDJ um lnvll HV1 G. A. H. KELLNR. Lens SYSTEM.

APPUCTION FILED FEB. 25| 1912.

GUSTAV A. H. KELLNEB, Ol' OPTICAL COIPANY, 0F

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LENS SYSTEI.

To all Iwhom z't may concern Be it known that I, GUs'rAv A. H. KELL-Nnn, of Rochester, in the county of Monroe and State of New York, haveinvented certain new and useful Improvements in Lens Systems; and I dohereby declare the following to be a full, clear, and exact descriptionof the same, reference being had to the accompanying drawings, forming-apart of this specification, lnerals marked thereon.

My invention has for its object to provide a lenssystem for telescopesof that type known as Galilean telescopes, particularly those of lowower, such as opera glasses, in which a field) of view is provided thatis larger than the field heretofore obtained in these instruments, the.lenses, at the same time, being so constructed that they are correctedfor curvature, astigmatism and distortion.

To these and other ends the invention consists in certain improvementsand combinations of parts, all as willbe hereinafter more fullydescribed, the novel features being pointed out in the claims at the endof the specification.

In the drawings: Figure 1 is a diagrammatic view 'of a lens system ofthe heretofore well known type, and prior art. Fig. 2 isa diagrammaticview illustrating the general appearance of the lens of a lens systemconstructed in accordance with my invenf tion.

In the illustration I have shown in Fig. 1 the common and well knownlens system employed in opera glasses, and' commonly telescope,comcalled the Galilean type of prising the eyepiece lens A tive lens B.The objective to Galilean telescopes is a let in which the adjoiningsurfaces are of like curvature and in which, like in all telescopeobjectives of this type, the collective elements are made of crownglass, and the dispersive elements of Hint glass. The crown glassordinarily used for Galilean telescopes has a refractive index for the Dline of about 1.54 and a v of about 58, while the flint glass has arefractive index of 1.62 and a v of 36. Y

If the powers of the collective and dispersive elements of the objectiveare in the right proportion the whole system (objective and eyepiece)will be achromatic and by varying theradii without changing the and theobjecusually applied doublet or trip- Speci'eation Letten Patent.

and to the reference-nu? Patented Sept. 12, 1916.

Application led February 26, 191B. Serial llo. 679,885.

power of the component it is possible to correct fordistortion. Alllother conditions beingthe same, the field of the Galilean telescope dends only upon the free diameter of the oV 'ective.

If the field of view obtained with a constructlon as described above, iskept under about eleven degrees for a power of 2, aberrations of obliquepencils: astigmatism, curvature of field, and distortion do notreachvobjectionable quantities. An attempt to increase the diameter ofthe objective and thereby gain in field proves a failure because theainin field is made worthless by the rapi increase of aberrations near themargin of the field which becomes intolerable and completely spoils thedefinition inthis part of the image. It canbe shown that theseaberrations can be removed by weakenmgthe negative power of the surfacesat which the different components of the ob- Jective adjoin.. This hasto be done by reducing the difference between the refractive indices ofthe glasses, while the difference of the vs is kept thesame. It can bedemonstrated that in this way, although theadjoining surfaces are no.longer available for use in the correction of distortion, thft thedistortion can be corrected simultaneously with astigmatism andcurvature of field' b shaping the outside surfaces of objective andeyepiece properly.

The best results are obtainable with re-v fractive indices essentiallythe same and not differing more than three per cent. from each other.

An example based upon the foregoing premises illustrating one embodimentof my invention and showing the kinds of glass, the thickness of thelenses, the curvatures and the distance between surfaces appears belowand may be considered as applying to the lenses shown in F 1g. 2.

Kinds of glass.

Radz', tltz'cmesav and distances.

r,=oo `.A Galilean telescope constructed in accordance with my inventiongives a well corrected eld of View, which is at least 1.6

times the size of that given by the type of lenses ordinarily employedin opera glasses. 5 I claim as my invention 1. A lens system for a.Galilean type telescope composed of an objective and an eye piece, theforward surfaces of the objective and eye piece having powersrespectively 10 between two and four times the power of the objective,the power of the other surfaces being resultant according to diameterand magnification to correct the lens system for astigmatism, curvatureof field and distor- 15 tion.

l 2. 'A compound objective lens fora Galilean type telescope composed ofelements of glass of different dis rsive power and of substantiallyequal in ices of refraction and provided with surfaces adapting saidobjec- 20 tive to coperate with an eyepiece lens, said objective andeyepiece lens being so shaped as to provide a field corrected forchromatic aberration, astigmatism, curvature of field and distortion.

GUSTAV A. H. KELLNER.

Witnesses:

G. WILLARD RICH, RUSSELL B. GRIFFITH.

